The present invention relates to an airlift discharge adaptor for a pneumatic vacuum conveyor and more particularly to such an adaptor which can be wheeled into position beneath a discharge door of a railroad hopper car by a single workman to facilitate unloading of pulverulent and granular dry material from the railroad car.
The discharge of granular materials from railroad cars has long presented a variety of problems. Traditionally a dedicated railroad siding was needed, often including a sunken pit beneath the railroad track in which was installed a gravity or mechanically operated conveyor. It was often inconvenient or even impossible to locate a plant near enough to such a siding to use the bulk unloading capabilities thereof.
More recently, pressure-type and vacuum-type pneumatic conveyors have been developed in which an adaptor is attached to the discharge doors of the railroad car. One or more pneumatic hoses are attached to the adaptor and the material is gravity-fed into the adaptor and conveyed away in the hoses via an airstream directed therethrough. While such pneumatic conveyors have represented a pronounced improvement over the fixed mechanical or gravity conveyors in sunken pits, a number of problems remain.
Such adaptors tend to be large and bulky, often requiring several workmen to lift and install them onto a railroad car. In addition, these adaptors must be tightly fitted to the car hopper doors and rigidly connected thereto. This is because, as the material is off loaded, the railroad car becomes lighter, thus rising under the influence of the spring suspension. The adaptor must rise with the car while maintaining the seal so that the material can be continuously off-loaded without spillage of the material.
At least two prior art attempts have been made to produce an improved and more conveniently handled discharge adaptor.
In U.S. Pat. No. 2,813,640 to Loomis, a wheeled discharge adaptor is provided with a hydraulic jacking arrangement such that the adaptor can be wheeled beneath the railroad car and mechanically raised to meet the hopper door. The hydraulic jacks are equipped with a manually operated jack handle disposed on the opposite side of the railroad car from the maneuvering handle for the adaptor itself. Material from the car hopper doors is gravity fed down an inclined chute to a rotary airlock. The airlock is placed in a pneumatic pressure line for conveying the material from the airlock. The resulting adaptor, with the hydraulic jacks, rotary airlock and air-activated gravity flow chute, is a large, complicated and very heavy conveyance. Furthermore, in order to operate the jacks, a workman would first need to roll the adaptor under the railroad car and then cross to the other side of the car where he would manually raise the jacks to position the adaptor under the hopper doors. Should the position of the adaptor need to be adjusted during jacking, the workman would need to repeatedly cross from side to side of the car to first adjust the position and then commence jacking again.
In U.S. Pat. No. 5,125,771 to Herman et al., a wheeled adaptor is positionable under a railcar to be unloaded. As in the Loomis patent, a pair of manually operated jacks can then be manipulated to raise the adaptor into position in contact with the railcar hopper door. The jacks in the Herman patent are mechanically operated screw jacks, including rotary handles which are positioned beneath the railroad car, thus requiring a workman to crawl beneath the car and physically crank the adaptor into position. In addition, the workman must alternate from side to side of the adaptor to incrementally raise the respective jacks to prevent the adaptor from tipping. The adaptor includes a rotary auger-type conveyor which carries material out an elongate tube to a pressure pneumatic or vacuum conveyor, where it is conveyed away. Again, as in the Loomis adaptor, the Herman adaptor is a ponderous and heavy piece of machinery which requires a workman to wheel it into position and then raise it manually via a set of screw jacks to mate with a hopper door. Unlike Loomis, with the screw jacks of Herman, no self-correcting leveling is accomplished as the railroad car rises. Thus, a workman would need to constantly adjust the screw jacks as the car rose, again necessitating crawling beneath the car and alternating from side to side of the adaptor.
Accordingly, a need still exists for a simple and reliable airlift adaptor for connecting to a railroad car to off load material therefrom. Such an adaptor should be capable of operation by a single workman, should include easily operated lifting jacks which permit the workman to conveniently and reliably position the adaptor beneath a railroad car to be unloaded, to raise the adaptor into contact with the car hopper door(s) and to unload the railroad car, all from a single, preferably standing, position.